All Electric Old Home — Part 2 — the data is in!
In March of 2022, I wrote about my experience taking my old home all-electric — you can read the Part 1 post. With 2022 in the rearview mirror, we have now completed a whole year as an all-electric house. Which means we now have data — both qualitative and quantitative! So let’s take a look.
Induction stove — My family has come to love the LG induction stove. Water for ramen noodles boils much faster, temperature controls for cooking are more fine-tuned than with gas, and there are no exhaust fumes. These are available for a tax credit under the new federal legislation that went into effect on Jan 1, 2023.
Hot water heater — The 80 gallon Richmond heat-pump water heater provides ample hot water for a family of five. I could count on one hand the number of times this year that we ran out of hot water (my teenage daughter accounts for each of those times). As a side benefit it dehumidifies the basement with no noticeable temperature effect. The water heater used 1,740 kWh of electricity in 2022 — providing all our hot water needs for a little over $200. The hot water heater EcoNet app provides lots of data on energy use and allows you to adjust the temperature controls, and even set it to vacation mode remotely, a feature I used on several occassions after leaving town and not remembering to set the temperature down while gone. Heat pump hot water heaters are also available for tax credit in 2023 — and have a short payback period.
Heat pump — The cold-weather heat pump from Mitsubishi /Trane kept our family comfortable year-round. Also available for tax credit in 2023 — along with tax credit for upgrading your electric panel if needed.
It used to be that summer used the most electricity — but now that the heat pump is heating the house peak energy use is clearly in the winter. HVAC accounted for nearly 70% of our electricity use in 2022. We have no natural gas bill and are saving the $30 a month base charge for gas service — saving $360 in 2022.
There are some adjustments we made along the way as we learned how the heat pump worked with our house. The heat pump takes longer to reach the set-point temperature — especially when heating. So we don’t drop the temperature as low during the day when we are at work/school or at night. The heat pump provides a more consistent temperature for the house in all seasons.
During the hottest part of the summer, when days were in the 90s and 100s and the nighttime temperatures stayed in the 80s, it took longer for the house to cool down in the evenings, especially on the southwest corner of the house where the master bedroom is located. The heat pump replaced an air conditioning unit that was 20+ years old, and uses much less energy to cool the house than the old unit.
We got to test the heat pump in extreme cold when the temperatures plummeted to below zero around Christmas. When it gets that cold and the temperature differential between the inside and outside gets to be 70 degrees or more (inside temp at 65 and outside temp at -5), the leakiness of the old house (built in 1910) is much more apparent, and it becomes harder to hold the inside temperature. The heat pump kept putting out heat, and we turned on the auxiliary electric resistance back-up.
The auxiliary resistance heat uses a LOT more electricity than the heat pump does. This is reflected in energy use during the peak cold days of nearly 4x the rest of the days in December. On the coldest day, December 23, the Auxiliary heat used 205kWh and the heat pump used 152 kWh. You can also see that consumption (orange) far exceeds solar production (blue) during December. The shift in electricity consumption patterns from summer to winter is an adjustment that utilities will have to make as the electrification of homes accelerates.
Electricity Use by Day — Dec 2022
Watching the house during the summer and winter extremes has reinforced the need to have additional air sealing done to tighten up the building envelope. The heat pump can deliver the warm and cool air needed to keep the house comfortable, but the conditioned air is quickly escaping through leaks in the building envelope. There are some clear areas to focus air-sealing on:
1) Rim-joist between the first and second floor — outside air is infiltrating the cavity between the joists that support the ceiling of the first story and the floor of the second story.
2) Roofline where the bay window roof attaches to the house
3) Roofline where the back porch attaches to the main house
4) Roofline where the front porch attaches to the main house
5) Old windows — re-doing the weatherstripping
Hiring a contractor to air-seal these areas would make an immediate impact on the comfort of the house and energy usage. It is also an expense that is eligible for a federal tax credit. I anticipate that effective air sealing could save a quarter of electricity usage — in large part by reducing the usage surges seen during extreme hot and cold.
Total Electricity Use and Costs
This chart shows overall electricity use in 2021 (blue) and 2022 (orange). You can see the change is seasonal electricity use with the heat pump providing heat starting in Oct 2021.
The Utility also provides a useful graph of electricity use against temperatures. You can see the increased use in the winter — and lower energy in the summer.
So how much did it cost to run our house off electricity? In 2022, we spent $2,540 on electricity for the full-year. Solar is providing around 1/3 of our energy so we can estimate that without solar our total electricity costs would be around $3,400.
In July, with the help of my daughter, I installed an Emporia energy monitoring system with the electric panel (hat tip to energyvanguard.com). It allows me to see the energy usage by specific circuits in the panel, and provides insight into what energy is being used for. As you can see from the chart below, heating and cooling the home is by far the biggest user of energy. This makes sense intuitively, but I was surprised by the magnitude of the difference between HVAC and everything else. I confess that it has also made me much less concerned about leaving an errant light on because as a % of energy use lighting is miniscule — especially with the house having LED lights throughout. You can also show it by cost (only half year of data).
Electricity use by circuit — July — Dec 2022
Solar — solar production started at the end of March 2022 so I don’t have a full year of data, but what we have so far provides useful information. Solar is providing about 1/3 of our home energy needs. The federal tax credit for solar remains in place and actually increases in 2023.
Electric Production and Consumption Mar — Dec 2022
In solar, siting, shade and orientation matter — as it turns out, it matters a lot. We saw significant variation among the panels. The panels facing west (the three on the left side of the array) produced less than the central southern facing panels. The four panels on the right faced south, but were affected by shade from a tree and a chimney.
The performance of the panels and our consumption patterns supported the decision to not install a battery system. Two-thirds of our energy still comes from the grid and our utility has net-metering, so its not worth it at this time.
Closing Thoughts
Moving to all-electric has made it much easier to understand our full energy use and cost picture. I now have much more granular data and controls that provides insights and allows for more active management of my home energy use.
After living with the new systems for a year, there are a few things I would do differently if I was doing it over again:
1) I would have waited to get a dehumidifier as part of the HVAC system. I had read that heat pumps sometimes are not as effective as keeping humidity low in the summer. This turned out not to be my experience (Midwest climate — could be different in the south or coastal area) and the heat pump kept the humidity comfortable. I should have held off on installing the dehumidifier until I saw how the system performed. The dehumidifier also consumes a lot of energy, so I mostly kept it turned off during the summer after I saw its energy draw using the Emporia energy monitor.
2) I would have installed an additional heat pump head unit installed in the master bedroom. The room sits on the southwest corner of the house and can get warm in the summer. Having a dedicated unit would have kept the room more comfortable but would have also allowed us to keep the rest of the house at a higher setpoint in the summer time since we were overcooling in order to keep the bedroom more comfortable. We may add another head unit in the bedroom this year. Although tightening up the building envelope would be a better long-term solution.
3) The control app for the system is a little finicky and took me a while to get it working right — part of that was my own curiosity in wanting to understand how to make it work — but in retrospect I should have sought some assistance from the installer to get it working right earlier.
When we made the decision to go all-electric in an older home, we were met with a lot of skepticism, particularly from people in the HVAC industry. A full year of using the system and measuring data how shown that it is possible to go all-electric without sacrificing comfort and performance. There has been a learning curve for sure, but we have no regrets and are pleased with how it is working.
